1. Field of the Invention
The present invention relates to a gas container of the type suitable for use for intermediately storing fresh gas in an anesthetic machine.
2. Description of the Prior Art
The use of gas containers for intermediate storage of fresh gas in anesthetic machines before the gas is sent to a breathing circuit is known. For simple regulation of the flow of fresh gas to the breathing circuit, the gas in the gas container is kept at constant pressure, around 100 cmH2O. Since the gas container usually contains a variable-volume reservoir, keeping the pressure constant is no simple matter.
One way to achieve a constant pressure, regardless of the prevailing volume, is to place a weight on the reservoir and allow gravity to exert a constant pressure on the gas in the container. This greatly increases the weight of the apparatus.
Another way is to use a relatively simple spring, with the reservoir""s variable-volume space being designed so that it compensates for variations in the spring""s compressive force on the reservoir whenever a wall of this space moves.
Other known ways entail the use of special resilient materials for the reservoir or spring designs producing a constant force within certain reservoir volume ranges.
Although these known methods for achieving a constant pressure do work satisfactorily, there is a need for additional alternative solutions. In particular, solutions combining good efficiency with simple design would be advantageous.
An object of the present invention is to provide a gas container for maintaining a constant gas pressure as an alternative to the known designs.
The above object is achieved in accordance with the principles of the present invention in a gas container having a gas inlet, a gas outlet, a variable-volume chamber connected to the gas inlet and the gas outlet, and a constant force applicator acting on the variable-volume chamber so that a constant gas pressure prevails therein, regardless of variations in the volume of the chamber, and wherein the constant force applicator is formed by a spring and a force transfer mechanism that interact with each other through a center of rotation and an application point, and wherein the force transfer mechanism varies the distance between the center of rotation and the application point dependent on variations in the volume of the variable-volume chamber.
In principle, constant force is obtained by the use of a spring and the force transfer mechanism that interact via a center of rotation and an application point, the center of rotation and the application point being arranged at a variable distance from each other. The ability to move e.g. the center of rotation makes direct compensation possible for variations in the spring force, by shifting the center of rotation. This also applies to the application point.